H3C Technologies H3C S7500E Series Switches - Manual (Page 313)

22-3
Table 22-2 Description of the fields in a SNAP-encapsulated LLDPDU
Field Description
Destination MAC
address The MAC address to which the LLDPDU is advertised. It is fixed to
0x0180-C200-000E, a multicast MAC address.
Source MAC address
The MAC address of the sending port. If the port does not have a MAC
address, the MAC address of the sending bridge is used.
Type
The SNAP type for the upper layer protocol. It is 0xAAAA-0300-0000-88CC
for LLDP.
Data LLDPDU
FCS
Frame check sequence, a 32-bit CRC value used to determine the validity
of the received Ethernet frame
LLDPDUs
LLDP uses LLDPDUs to exchange information. An LLDPDU comprises multiple type, length, and value
(TLV) sequences. Each carries a specific type of device information, as shown in
Figure 22-3 .
Figure 22-3 LLDPDU encapsulation format
An LLDPDU can carry up to 28 types of TLVs. Mandatory TLVs include Chassis ID TLV, Port ID TLV,
Time To Live TLV, and End of LLDPDU TLV. Other TLVs are optional.
TLVs
TLVs are type, length, and value sequences that carry information elements. The type field identifies
the type of information, the length field measures the length of the information field in octets, and the
value field contains the information itself.
LLDPDU TLVs fall into these categories: basic management TLVs, organizationally (IEEE 802.1 and
IEEE 802.3) specific TLVs, and LLDP-MED (media endpoint discovery) TLVs. Basic management
TLVs are essential to device management. Organizationally specific TLVs and LLDP-MED TLVs are
used for enhanced device management; they are defined by standardization or other organizations
and thus are optional to LLDPDUs.
1) Basic management TLVs
Table 22-1 lists the basic management TLV types currently in use. Some of them must be included in
every LLDPDU.
Table 22-3 Basic LLDP TLVs
Type Description Remarks
Chassis ID Bridge MAC address of the sending device Mandatory